Doors of the type used for closing a large opening in a building, such as a garage door, have long been manufactured using a plurality of substantially identical panels. The plurality of panels are typically hingedly connected together to permit relative hinging movement between adjacent panels when the door is moved between a closed vertical position and an open horizontal position. Such multi-panel doors, commonly referred to as sectional doors, often employ individual wooden panels which are appropriately hingedly connected at the adjacent horizontal edges thereof. Wooden panels are costly to manufacture, however, and result in the door being extremely heavy, particularly when the door is of large size. The weight of wooden sectional doors makes opening and closing of the door extremely difficult, even when an automatic operator is used.
In an effort to improve upon wooden sectional doors, panels which are rolled or formed from a tin sheet material, such as metal, fiberglass, or plastic have been used. These rolled or formed panels are necessarily provided with some form or irregular cross-section, such as a channel shaped cross-section, to provide the panels with sufficient strength and rigidity. Doors using formed or rolled panels have proved acceptable in some situations, but suffer from the distinct disadvantages that they are extremely heat conductive leading to thermal losses when used with an air-conditioned space.
Another improved door panel construction has been used having inner and outer thin sheet material skins and an insulating core, resulting in a construction which is light in weight, thermally insulated, and highly warp-resistant over relatively long spans. This improved construction is designed to be made by a continuous and automated "foamed-in-place" process where two cells of metal or vinyl material are uncoiled in a vertically spaced relationship, edge-formed to a desired configuration, and brought together at a foam-injecting station. Liquid polyurethane foam material is then placed in the lower skin at the foam-injecting station, and the skins are held in a spaced-apart relationship by a pressure conveyor while the foam cures. At the end of the pressure conveyor, the emerging continuous strip of door panel structure is cut transversely to desired lengths.
In the prior art foamed-in-place manufacturing process, wherein the two continuous rolls of panel skin material are used, the lower skin material is typically first rolled up on the edges to form a trough longitudinal in the direction of transport of the skin material. The unexpanded, liquid foam material is then applied in the center of the trough and spread evenly across the interior surface of the trough. Meanwhile, the upper skin material is suitably edge formed and transported to an opposing relationship with the trough-shaped lower skin material holding the expanding liquid foam material. The upper skin material, lower skin material and partially expanded foam enter a pressure conveyor which constrains the skins on all sides to enable dimensional integrity while the foam cures. At the end of the pressure conveyor, the foam is fully cured, and the adhesive characteristics of the foam maintain the structural integrity of the panel. It is known to incorporate longitudinal ornamental features such as ribs into panel skins through a continuous rolling process, at or near the edge forming step of the process.
The prior art continuous foamed-in-place door panel manufacturing process uses continuous rolls of material to form the upper and lower skins. A major disadvantage of this system is that the use of continuous skin materials prohibits the incorporation of intermittent transverse ornamental features such as "raised panels" into the skins. Such features can be practically incorporated into a skin only by processes such as stamping or embossing the skin where the skin is intermittently held stationary. It has not been practical to incorporate a step into the overall foamed-in-place manufacturing process where a continuous skin material can be maintained stationary on an intermittent basis in order to emboss or stamp a transverse ornamental feature.
Another problem in adapting transverse features to the foamed-in-place process arises from difficulty in handling the skins due to their fragility in the unmanufactured state. For example, once sheet steel is embossed with an ornamental feature, longitudinal or transverse, it cannot be rolled into a continuous roll without permanently kinking the sheet.
It is also believed to be impractical to adapt the continuous foamed-in-place process, where the timing of the foam material injection and pressure containment of the skins panel during foam curing is critical, to a stamping or embossing process "on the fly". On the fly stamping or embossing would involve embossing the transverse ornamental features on the sheet as it is removed from a roll and immediately prior to entering the portion of the process where foam is sandwiched between the upper and lower skins. A stamping or embossing process using a press requires that the material intermittently be held stationary for a given cycle time during which the stamping or embossing process is performed. Rotary embossers are also believed to be impractical, as well, due to the tendency of such embossers to leave undesirable surface defects ("oil-canning") on the embossed product.
The industry has been frustrated in attempting to adapt the continuous foamed-in-place panel manufacturing process to make panels having intermittent transverse ornamental features. Thus, it can be seen that a need has arisen for a continuous foamed-in-place door panel manufacturing process that enables the use of panel surfaces that include intermittent transverse ornamental features.